The aims of this proposal concern the development and application of Open Path -Fourier transform infrared (OP-FTIR) remote sensing technology to workplace air monitoring. As shown by our previous studies, the development of OP-FTIR sampling methods must address the nature and utility of this technique in the context of personal exposure monitoring. Over the past years of this project we have developed the underlying sampling framework for using fixed beam OP-FTIR for area monitoring and steerable beam OP-FTIR to obtain spatial information for exposure monitoring. This proposal will continue this work with strong emphasis on developing methods for using multiple steerable beam geometry to assess personal exposures. This proposal also calls for field studies to evaluate the OP-FTIR methods developed in the previous years of this research project. The primary objectives of this project are: (1) Conduct chamber studies using human subjects to develop and evaluate methods for estimating personal exposures with OP-FTIR spectroscopy using a multiple scanning beam system; (2) Assess sampling strategies for rapidly locating sources and areas of high concentration gradients in chamber studies using movable beam hardware and human subjects performing simulated work tasks; (3) Evaluate in field trials methods for using multiple beam OP-FTIR data to detect departures from normal operating conditions, as an advanced form of area monitoring for exposure control; (4) Investigate scanning beam methods for gathering data suitable for computed tomographic reconstruction of concentration fields under practical conditions; (5) Conduct field testing to verify the reliability of OP-FTIR monitoring methods for estimating the upper bound in personal exposures, with particular emphasis on predicting Short Term and Ceiling exposure limits for workers. The development of OP-FTIR realtime monitoring technology for workplaces is important to Industrial Hygiene (IH) practice for two reasons: (1) accurate routine exposure assessment is crucial to IH decision-making, and (2) the lack of reasonable alternative sampling methods for labile, volatile, or polar compounds alone or when they occur as components in complex mixtures. Ongoing exposure characterization is a central feature of IH practice in that it guides decisions about regulatory compliance, health risks, and the allocation of resources for intervention.